Assistant's features are far from consistent across platforms and have been like that since the service's launch. Some commands work on phones but not speakers, others vice-versa, not to mention smartwatches, TVs, cars, Bluetooth headsets, and other types of devices. Here's another example of this fragmentation: Routines aren't working on Auto. In fact they haven't been supported for over a year and there's no solution on the horizon.
More than a year ago, routines were perfectly functional on Android Auto. Whether you used them to trigger your Leaving home, Commuting home, Commuting to work, or any custom-made routine while you were driving, Assistant answered correctly and executed all commands. Then, around October 2018, it stopped working, seemingly on both phones and car head units. The feature had been buggy for a few users already, but it wasn't until October that reports of Assistant answering "Routines aren't currently supported on this device" started flowing in. And there have been many, many, many, really many complaints about this across various forums and support threads since.
Same routine asked on Assistant on the phone (with answer) and 4 times on Auto (no answer).
Even if your routine is something as benign as replacing a couple of words (i.e. no smart home gear, no sending messages or making calls), it doesn't work. In the example above, you can see me try it with a routine that replaces "what's the weather at work" with "what's the weather in Ballouneh, Lebanon" (to avoid confusion with balloons). It works on my Pixel 4 XL, on my smart speakers and displays, but when I try it from Android Auto on my Pixel 4 XL, I get told that routines aren't supported on this device. It's a weird limitation that doesn't make sense.
Bluetooth, Do Not Disturb, Digital Wellbeing, app updates, and other culprits have been theorized by users, but none of these seem to be responsible. Many "solutions" have been suggested too, but again, none really work at this point. It looks like a blanket "no routines in Auto" rule has been set up by the Assistant and/or Auto teams and you can't circumvent it.
This isn't the first bug we've pointed out in Assistant on Android Auto — the platform seems to have drawn the short stick of Assistant's mess-ups — but it's certainly one of the oldest ones. Google has also been mum about this with no explanation or timeline for a fix. We've reached out to the company and will let you if and when we hear back.
Good news and bad news: Google has responded to our inquiry, and has confirmed our findings that routines aren't supported on Android Auto right now — so the company is at least aware of this limitation, and it's not some bug slipping by under the radar.
While that's something, Google also isn't giving us any indication that this is a problem we can expect to see fixed in the near future. At best, we're told that the company will share more details when it's ready, but we're not getting any specifics for now.